Fibonacci Prime Test
Check if a number is both a Fibonacci number and a prime. Runs entirely in your browser, so your data never leaves your device.
0 chars · 0 lines
Output
The result appears here as you type.
How to use Fibonacci Prime Test
- 1. Paste your numbers. Enter the numbers you want checked, one per line, into the input pane, for example 5, 8 and 7.
- 2. Understand the two-part check. Each number is tested against both conditions at once: whether it belongs to the Fibonacci sequence and whether it's a prime number, since a Fibonacci prime must satisfy both.
- 3. Read the classification for each number. The output labels each number as a Fibonacci prime, or explains which condition failed, such as being Fibonacci but not prime, or prime but not Fibonacci.
When to use Fibonacci Prime Test
Fibonacci Prime Test checks whether a number satisfies both properties at once: it must sit inside the Fibonacci sequence and also be a prime number. These rare doubly-qualified numbers, like 2, 3, 5, 13 and 89, come up often in recreational number theory.
- Studying an intersection-of-properties problem. A number theory course covers numbers that satisfy two conditions simultaneously, and checking real examples against both the Fibonacci and prime tests reinforces the concept.
- Building a puzzle around rare number properties. A puzzle hunt or trivia round wants players to find numbers that are both Fibonacci and prime, and checking candidate answers confirms which ones actually qualify.
- Writing test cases for a combined-property function. You're implementing a function that flags Fibonacci primes and need known true and false cases across both dimensions to validate the logic thoroughly.
- Investigating why a candidate number fails. You suspected a number was a Fibonacci prime but it isn't, and the explanation clarifies whether it failed the Fibonacci test, the primality test, or both.
Examples
Testing several numbers
Input
5 8 7
Output
5 is a Fibonacci prime 8 is not a Fibonacci prime (Fibonacci but not prime) 7 is not a Fibonacci prime (prime but not Fibonacci)
A larger Fibonacci prime
Input
28657
Output
28657 is a Fibonacci prime
About the Fibonacci Prime Test tool
Fibonacci Prime Test runs as plain JavaScript in your browser tab, with no server behind it. Check if a number is both a Fibonacci number and a prime. Whatever you put in stays on your device from start to finish.
The tool is part of EditSafely's Number Tools section, 194 single-purpose utilities built around the same idea: open the page, get the result, keep your data to yourself.
There is nothing to configure. Provide the input and the result appears on its own. 2 worked examples further down the page show exactly what the tool produces for real inputs.
That local-first design has practical benefits beyond privacy. The tool keeps working on a flaky connection once the page has loaded, results are instant because nothing round-trips to a server, and it is safe to use with confidential material.
Frequently asked questions
Does Fibonacci Prime Test cost anything?
Yes, it is completely free. All 2,658 tools on EditSafely work without an account, a subscription or usage limits.
Is it safe to paste sensitive or confidential data?
No data leaves your device. The whole tool is JavaScript that runs inside your browser tab, so there is no upload, no server-side processing and no log of what you did. If you disconnect from the internet after the page loads, it keeps working.
How much text can I process at once?
There is no fixed limit. Because the work happens on your own device rather than on a shared server, the practical ceiling is your machine's memory, which comfortably handles inputs far larger than typical online tools allow.
Do I need to sign up or install anything?
Nothing to install and no account needed. Open the page in any up-to-date browser, including on a phone or tablet, and the tool is ready.
How do I use the result?
The output panel has a one-click copy button, and you can keep refining the input while you work; the result updates in place as you type.